1. Field of the Invention
The present invention relates to a multi-wavelength light-emitting module, and particularly relates to a multi-wavelength light-emitting module that has a plurality LED array with different wavelengths sharing an optical system of an optical amplifier.
2. Description of the Related Art
In the typical printer technology, a laser is used as a light source in a printer head to scan and transfer the printing information as light signals to a rotating drum in order to generate electrostatic latent images formed on the rotating drum. Moreover, the printing method further includes a toner absorbing step, a transferring step, a hot pressing step, an electrostatic discharging step etc. to achieve printing. However, a laser printer head of the prior art has many optical components, and the mechanism of the laser printer head is complex and the optical path of the laser printer head is very long. Hence, the optical structure is quite complex and difficult to reduce in size when using a laser as light source. Therefore, the current trend is toward using light emitting diodes to replace lasers as light sources in printer heads, which can simplify the optical structure.
A further requirement is to reduce the volume of each light emitting diode so as to increase the resolution of the printer. The number of light emitting diodes per unit area in the printer head can be increased when the volume of each light emitting diode is reduced. According to the typical packaging method, a highly precise packaging apparatus is required to arrange the light emitting diode arrays and the driver integrated circuits so that they are exactly parallel to each other in a printed circuit board. Then, if the resolution of the printer is 600 dpi (dots per inch) on A4 size paper, about 5000 wires are formed between the light emitting diode arrays and the driver integrated circuits by means of a wire bonding process. The driver integrated circuits drive the light emitting diode arrays through these wires.
The necessity for a highly exact and dense wire bonding process in the foregoing method increases the difficulty of the packaging process. This reduces the product yield and indirectly raises manufacturing costs. Moreover, the above-mentioned technology of the prior art can not manufacture electrical connections with high density between an LED (Light Emitting Diode) array and a drive IC (Integrated Circuit) array, so a packaged multi-wavelength light-emitting module of the prior art that has a plurality LED array sets with different wavelengths can not share an optical system of an optical amplifier. In other words, each LED array set of the prior art needs to mate with a corresponding optical amplifier. This increases the size of the packaged multi-wavelength light-emitting module of the prior art, and thus also increases the size of printers using the packaged multi-wavelength light-emitting module of the prior art